CEL that goes away when I plug in laptop?

[jeff122886]

I have been having an issue with the daughterboard communication light, i recently had my alternator crap out on me and replaced it. The light will go away when I plug in my laptop, then the car idles rough. I turn it off then on and it runs fine but will randomly cut out and sometimes while driving the light comes back. I also can't clear security or upload a tune anymore. I checked cranking voltage and it was around 10.5V-11.5V, think my battery needs to be replaced as well?

[Hondata]

You have a bad ground somewhere and the ECU is grounding via USB & the laptop.

Do not plug in the USB cable until you fix this problem otherwise the ECU and/or KPro traces will be damaged from the current.

[jeff122886]

You have a bad ground somewhere and the ECU is grounding via USB & the laptop.

Do not plug in the USB cable until you fix this problem otherwise the ECU and/or KPro traces will be damaged from the current.

same thing happens with the USB unplugged. can I run a new ground from the pin?

[Spunkster]

Try the ECU in a known working vehicle. If it works without any problems then you know there is a problem that needs to be resolved with your wiring. IF it still does not work correctly then your ECU my be damaged by the faulty wiring that is in the vehicle and you will need to correct the wiring fault before replacing or repairing your ECU/K-Pro.

[jeff122886]

Try the ECU in a known working vehicle. If it works without any problems then you know there is a problem that needs to be resolved with your wiring. IF it still does not work correctly then your ECU my be damaged by the faulty wiring that is in the vehicle and you will need to correct the wiring fault before replacing or repairing your ECU/K-Pro.

ok will give that a try when I get a friend who is free. do you know what pin I could check ground continuity on? I used to have a pinout diagram in my favorites but the link seems to have been taken down.

[Spunkster]

http://www.hondata.com/help/kmanager/ecuconnectors.htm

[jeff122886]

http://www.hondata.com/help/kmanager/ecuconnectors.htm

still having issues with this, going to try my ECU in my friends car tomorrow. I did try his battery a couple months ago and it started fine and let me upload with no issues but now i tried again and it still does the same thing? the ecu should not share a ground to the chassis correct? any pins that should show ground? I used a multi-meter from battery ground to tranny and had about .5 ohms and same with cylinder head, starter armature, pass motor mount, is there anywhere else I should check??

also, when I have the USB plugged in to the laptop without being in on the ONII position I get the option to upload/datalog, etc... this is only supposed to happen when I turn key to ONII position right?

[jeff122886]

also, when searching I found this link

http://www.hondata.com/forum/viewtopic.php?t=11280

I got my K-Pro in 2007 from Wangs Auto, I actually randomly would get a CEL (daughterboard communication) and after wiggling my cord behind ECU the code would go away (even if I had no laptop hooked up), maybe this is just a loose USB connection on the kpro board that finally broke free? gonna pop the ECU out when I get home and see if i can see anything

[Hondata]

You cannot use a digital multimeter to establish if a ground is ok, because the resolution of the multimeter is much more than the resistance should be. You need to remove all the grounds and clean down to bare metal under the connector.

If you open up the ECU then post photos of the top and bottom of the circuit board to show us the soldering.

[jeff122886]

You cannot use a digital multimeter to establish if a ground is ok, because the resolution of the multimeter is much more than the resistance should be. You need to remove all the grounds and clean down to bare metal under the connector.

If you open up the ECU then post photos of the top and bottom of the circuit board to show us the soldering.

So I tried my ECU today in a friends RSX and the same thing happens. Not able to upload, not able to clear security and with the key not even in the ignition it shows the Ignition on. I popped open the cover to take a look inside and there were a couple light brown spots on the ECU board, not sure if anything fried or not. I did take a look at the connections that were soldered in by Wang, the actual KPRO ones looked ok but I could not tell on the ECU side because they are smothered with hot glue.

Think the ECU is fried or maybe loose connections w/ Kpro or maybe even the Kpro fried?

What is my next course of action? Thanks. Should I just give you guys a call tomorrow?